1. Field of the Invention
The present invention concerns a disposable sampling device for an apparatus for counting particles contained in a liquid, such as blood cells in a blood sample and yeast fungus in wort, according to the preamble of claim 1.
2. Description of Background Art
It is known in the state of art to count blood cells by causing a volume of diluted blood sample to pass a so-called capillary, i.e., an extremely small hole, generally in a ruby, the hole having a diameter considerably larger than the size of a blood cell, typically 80 xcexcm. A voltage is applied over the capillary, and, when a blood cell passes through the hole, the electrical resistance changes. This is because the cells can be regarded as insulators. Each change in resistance can be detected by suitable electronic equipment, and the sum of all changes detected corresponds to the number of blood cells having passed through the capillary. In order to obtain the concentration of cells in the original sample, the concentration of cells in the diluted sample is multiplied by the dilution factor, typically 1:40000 when counting of red blood cells (RBC) is concerned. It is obvious, that measuring of sample volumes and dilution liquid volumes must be performed in an accurate and repeatable way such that not only a correct degree of dilution can always be guaranteed but also a thorough and uniform mixing of the two volumes is ensured.
In a typical state of art apparatus, used for counting blood cells, a syringe is employed for providing a defined volume (typically 5 ml) of diluting liquid, and this volume is displaced through a conduit to a measuring chamber. On its way to the measuring chamber, the diluting liquid brings with it a defined volume (typically 25 xcexcl) of blood sample previously introduced into the conduit. The blood sample mixes with and is diluted by the diluting liquid in the measuring chamber, which is, thus, also a dilution or mixing chamber, and a defined fraction of the diluted sample is further displaced through a capillary located in a wall of the measuring chamber, or, in a transducer located within the measuring chamber. In this state of art device, all components, except a vessel containing a blood sample, are permanently included in an apparatus containing also electronic equipment needed for counting particles and performing calculations necessary for obtaining resulting concentration values. Consequently, all components contacted by blood must be thoroughly cleaned after each counting procedure, such as by flushing with a suitable rinsing liquid. Also, this device is expensive and rather cumbersome, and, therefore, does not lend itself to use outside more well-equipped and established medical institutions, such as hospitals, public health centres and larger private surgeries.
There is a need, thus, to provide a relatively cheap and simple device for sampling, e.g. a blood sample or a wort sample, for use with a more stationary particle counting apparatus. The sampling device shall be useful outside medical institutions of the general kind mentionedxe2x80x94as regards blood samplingxe2x80x94as well as in breweriesxe2x80x94as regards wort sampling. It shall also be easy to handle even by relatively unskilled personnel, and all its components contacted by a sample shall be contained within a disposable housing. The housing shall not contain expensive components, such as electronic equipment for the actual particle counting and evaluating purposes.
The present invention has as its object to provide a sampling device that fulfills the above need.
To achieve this, the present invention suggests a disposable sampling device for an apparatus for counting particles contained in a liquid, comprising a solid block-shaped housing connectable in a defined position to said apparatus, said housing having therein means for introducing a sample into said housing; means for metering a defined volume of said sample; means containing a defined volume of a diluting liquid; means defining a diluting chamber; means for simultaneously directing said defined volume of said sample and said defined volume of said diluting liquid to said diluting chamber for obtaining therein a diluted sample; means for directing at least a portion of said diluted sample past particle detecting means; signal transmitting means connecting said particle detecting means and terminal means located at an outer boundary of said housing in a position corresponding to a location of terminal means of said apparatus when said housing is connected thereto in said defined position.